In a pumping fluid well, such as an oil well, the oil from the well formation flows into a well conduit and to the pump where it is then pumped to the well surface. However, it is sometimes desirable to shut off the flow of oil from the formation such as during workover operations. However, even with the pump turned off, the oil from the formation will continue to flow due to formation pressure and rise therein and interfere with workover operations.
It is known, as disclosed in U.S. patent application Ser. No. 06/645,574, filed 08/29/84, now U.S. Pat. No. 4,721,162, entitled "Fluid Level Controlled Safety Valve" to use the hydrostatic pressure created by the liquid level of the production liquids in a well conduit to shut off the flow of well production when the well pump is stopped. However, in such a system, the valve blocked the well conduit and had to be removed before wireline operations in the well could be performed below the location of the valve.
The present invention is directed to a liquid level actuated sleeve valve for use in a well tubing in a well casing in which the valve is actuated between open and closed positions by the hydrostatic pressure of the liquid level in the well annulus. Normally, the seals in sleeve valves have the disadvantages of (1) high friction, and (2) limited life caused by cycling of the sleeve over and damaging the seals. However, the present invention is directed to providing seals which have low friction and which are set and released to minimize seal damage.